JP6731543B2 - How to discharge an electrical energy store - Google Patents

Description

The present invention relates to a method of discharging an electrical energy store. A large amount of energy can be stored in an electrical energy store (eg, an electric capacitor). It is difficult to control these large amounts of energy when a failure occurs. This is because in the event of a failure, energy can be released uncontrolled and suddenly resulting in a change to another form of energy. In doing so, electronic circuits or electronic components (e.g., power semiconductors) connected to the electrical energy store often cannot accept and suppress these emitted amounts of energy. This leads to a complete destruction of the electronic circuit when a failure occurs, for example by an explosion. Furthermore, when an electronic circuit is destroyed, a secondary failure may occur in adjacent equipment. Causes of such secondary failures are, for example, arcs, large magnetic current forces, or strong pollution due to the above-mentioned explosion.

From US Pat. No. 6,037,099 a short circuit current release device is known for submodules of a modular multilevel converter. In this short-circuit current release device, a thyristor is connected in parallel with the electric capacitor. This is because when a failure occurs, the discharge current of the electric capacitor is controlled and bypassed by the thyristor to protect the electronic circuit connected to the electric capacitor. This known short-circuit current release device has an electronic evaluation circuit, which recognizes the presence of a fault and supplies a gate current to the gate terminal of the thyristor in the presence of the fault, whereby the thyristor. Turn on (fire). Additional electronic components are essential to implement this evaluation circuit, which requires some time to recognize a fault and supply the gate current to the thyristor. Furthermore, the evaluation circuit reduces the reliability of the protection element, ie the short-circuit release device.

International Patent Application Publication No. 2013/044961

The object of the present invention is to provide a method and a device for discharging an electrical energy store without the need for an additional evaluation circuit.

This problem is solved according to the invention by a method and a device according to the independent claims. Advantageous embodiments of the method and the device are described in the dependent claims.

Disclosed is a method of discharging an electrical energy store connected to an electronic circuit by a first electrical conductor and a second electrical conductor, wherein a thyristor for discharging the energy store is provided. To do. In this way,
-On the basis of a fault occurring in the electronic circuit (in particular, due to a short circuit occurring in the electronic circuit), the discharge current of the energy store begins to flow from the energy store through the first electrical conductor into the electronic circuit, Return to the energy store via the second electrical conductor,
A time-varying magnetic field is generated around the first and second electrical conductors based on the (increasing) discharge current, the time-varying magnetic field causing the semiconductor material of the thyristor to Penetrate,
・The time-varying magnetic field induces (applies) an electric current (eddy current) in the semiconductor material of the thyristor,
• (Exclusively) this induced current turns on the thyristor, which causes the discharge current of the energy store to flow through the turned-on thyristor, thereby bypassing the electronic circuit.
Thus, the turned-on thyristor takes on the energy storage discharge current (at least a portion of the energy storage discharge current), ie the turned-on thyristor bypasses the energy storage discharge current. The energy store may be, for example, a capacitor-type energy store, for example a battery, a battery or a battery. The induced current can act as a gate or firing current in the thyristor. The gate current is the current that flows through the gate semiconductor structure of the thyristor and turns on the thyristor. The ignition current is a current that flows inside the thyristor outside the gate semiconductor structure of the thyristor and turns on the thyristor.

In other words, the induced current (eddy current) turns on the thyristor. Thereby, the discharge current of the energy store bypasses the electronic circuit and flows through the turned-on thyristor. The thyristor may be spatially arranged adjacent to the first electrical conductor and/or the second electrical conductor.

In this method, the time-varying magnetic field (generated due to the increasing discharge current of the energy store) is used directly to turn on (ie ignite) the thyristor. Therefore, no additional components or evaluation circuits are required. Thereby, this method can be implemented very simply, cheaply and reliably. Furthermore, a time delay at turn-on of the thyristor is avoided. (Evaluation circuits in which additional electronic components are present are, of course, necessarily accompanied by such a delay.) Therefore, this thyristor is designed for additional detection or firing within the additional evaluation circuit. A self-igniting thyristor without additional switching delay based on the electronics for the thyristor (in this case, the thyristor's ignition delay time remains unchanged. The thyristor's ignition delay time is generally a few μs. , Typically 1-3 μs). Due to the absence of additional components and additional evaluation circuits, no additional electrical losses occur. Especially in the case of power electronics installations where there are a large number of electrical energy stores (as in the case of modular multi-level converters for example), the electrical losses are thereby worth mentioning. It can be reduced. Thereby, the energy efficiency of the equipment can be improved. In the case of the method described above, a small electrical loss occurs due to the leakage current of the thyristor. This leakage current is generally very low.

Therefore, the above-mentioned method enables a large cost saving and a reduction in failure rate (FIT value, FIT=failure in time) based on avoiding additional electronic components or avoiding additional electronic evaluation circuits. .. Since the non-existent components do not fail, the probability of failure occurrence is clearly reduced.

The method can proceed such that the induced current causes the thyristor to turn on when the temporal change in the magnetic field exceeds a threshold value. This threshold value is significantly influenced by the choice of the spatial arrangement of the thyristor with respect to the first electrical conductor and/or the second electrical conductor. In order to generate a sufficiently strong temporal change of the magnetic field for the turn-on of the thyristor, for example, the greater the distance between the thyristor and the first electrical conductor or the second electrical conductor, the greater the discharge current The change over time must be even greater. In other words, the method can proceed such that when the change in discharge current over time exceeds a threshold value, the induced current turns on the thyristor.

The method can be configured such that the electronic circuit has at least two (on/off controllable) electronic switching elements arranged in one half bridge circuit (the half bridge circuit is It is connected in parallel to the accumulator). Electronic circuits of this kind are contained, for example, in so-called half-bridge submodules of modular multilevel converters.

The method can also be arranged such that the electronic circuit comprises said two electronic switching elements and two other (on/off controllable) electronic switching elements, in which case two electronic switching elements are provided. The switch element and the two other electronic switch elements are arranged in one full bridge circuit. Such electronic circuits are contained, for example, in so-called full-bridge submodules of modular multilevel converters.

Further, an electronic circuit, an electrical energy store connected to the electronic circuit by a first electrical conductor and a second electrical conductor, and a thyristor for discharging the energy store (when a failure occurs). And the thyristor is arranged spatially adjacent to the first electrical conductor and/or the second electrical conductor as follows. That is, a time that is generated based on a discharge current of the energy store flowing through at least one electrical conductor (eg, a first electrical conductor and/or a second electrical conductor) to penetrate the semiconductor material of the thyristor, So that a current (eddy current) that turns on the thyristor is induced (applied) in the semiconductor material of the thyristor (when the temporal change of the magnetic field exceeds a threshold value) based on a magnetic field that changes in a time-dependent manner. It is arranged spatially adjacent to the first electrical conductor and/or the second electrical conductor. In that case, the energy store may be, for example, a capacitor-type energy store, for example a battery, a battery or a battery. The induced current can act as a gate or firing current in the thyristor. This device has the same advantages as described above in connection with the method.

The device may also be arranged such that the thyristor is arranged in the intermediate space between the first electrical conductor and the second electrical conductor. In the case of this device, the thyristor is penetrated very well by the magnetic field of the first electrical conductor and by the magnetic field of the second electrical conductor.

The device can also be configured such that the anode of the thyristor is (conductive) connected to the first electrical conductor and the cathode of the thyristor is (conductive) connected to the second electrical conductor. In other words, the thyristor may be directly connected between the first electric conductor and the second electric conductor. In that case, only two contact sites are required: a first contact site between the anode and the first electrical conductor and a second contact site between the cathode and the second electrical conductor.

The device can also be configured such that the thyristor is mechanically fixed between the first electrical conductor and the second electrical conductor. (The first electric conductor, the thyristor and the second electric conductor form a holding frame). Due to its mechanical fastening, advantageously a good electrical contact between the first electrical conductor and the thyristor (more precisely the first electrical conductor and the anode of the thyristor) and a second electrical contact Good electrical contact between the electric conductor of the thyristor and the thyristor (more precisely, between the second electric conductor and the cathode of the thyristor) is ensured.

The device can also be configured such that the thyristor has a disk cell container. A thyristor of this kind with a disk cell container can advantageously be mechanically fixed between the first and the second electrical conductor in a particularly simple manner.

The device can also be configured such that the first electrical conductor and/or the second electrical conductor are each formed as a current rail. A current rail of this kind makes it possible, on the one hand, to safely guide large discharge currents of the energy store, and on the other hand, a (mechanically stable) current rail ensures a secure mechanical fixing of the thyristor.

The device comprises a first electrical conductor and/or a second electrical conductor each having a flat outer surface, the semiconductor material of the thyristor forming a disc (wafer), the disc having at least a flat outer surface. It can also be configured to be arranged parallel to one side. (In that case, in particular, the first electrical conductor has a first flat outer surface, the second electrical conductor has a second flat outer surface, and the first flat outer surface has a second flat outer surface. Arranged parallel to the outer surface, the semiconductor material of the thyristor forming a disk (wafer), which disk is arranged parallel to the first flat outer surface and the second flat outer surface). Such a device advantageously allows a small distance between the first and second electrical conductors. Thereby, a particularly strong magnetic field can be generated between the first electric conductor and the second electric conductor. Furthermore, in this type of device, the time-varying magnetic field penetrates the semiconductor material of the thyristor particularly well, so that a current (for example acting as a gate current) is reliably induced in the semiconductor material of the thyristor. It

The device may also be configured such that the thyristor is coupled to the energy storage device with low inductance (in which case the electrical connection between the energy storage device and the thyristor is the energy storage device and the electronic circuit). Has a smaller electrical inductance than the electrical connection between. In that case, after the thyristor is turned on, the discharge current of the energy store flows through the thyristor and not through the electronic circuit (or only to a very small extent).

The device can also be configured such that the thyristor is connected in parallel with the energy store. This allows the thyristor to be placed very closely in the energy store, which allows a particularly low-inductance electrical connection between the energy store and the thyristor.

The device can also be configured such that the electronic circuit has at least two (on/off controllable) electronic switching elements arranged in one half-bridge circuit (in which case the half-bridge circuit). Is connected in parallel to the energy store). Electronic circuits of this kind are contained, for example, in so-called half-bridge submodules of modular multilevel converters.

The device can also be configured such that the electronic circuit comprises the two electronic switch elements and two other (on/off controllable) switch elements, in which case the two electronic switch elements. The element and the two other switching elements are arranged in one full bridge circuit. Electronic circuits of this kind are contained, for example, in so-called full-bridge submodules of modular multilevel converters.

Disclosed is a module of a modular multi-level converter having a device according to one of the variants described above.

Further, a modular multi-level converter having a large number of such modules is disclosed.

The method and apparatus described above have the same or similar advantages.

Hereinafter, the present invention will be described in more detail based on examples. The same code|symbol refers to the element which has the same element or the same action.

FIG. 1 is a diagram showing an embodiment of a power conversion device having a large number of modules. FIG. 2 is a diagram showing an example of one module. FIG. 3 is a diagram showing another embodiment of one module. FIG. 4 is a diagram showing an example of high-voltage DC transmission equipment. FIG. 5 is a diagram showing an embodiment of a reactive power compensator. FIG. 6 is a diagram showing an embodiment of a module having one thyristor. FIG. 7 is a diagram showing another embodiment of a module having one thyristor. FIG. 8 is a plan view showing an example of the mounted thyristor. FIG. 9 is a side view showing an embodiment of the mounted thyristor. FIG. 10 is a diagram illustrating a semiconductor material of a thyristor in a magnetic field. FIG. 11 is a diagram illustrating a method process.

In FIG. 1, a power converter 1 is shown in the form of a modular multilevel converter (MMC). This multi-level converter 1 has a first AC voltage terminal 5, a second AC voltage terminal 7 and a third AC voltage terminal 9. The first AC voltage terminal 5 is electrically connected to the first phase module arm 11 and the second phase module arm 13. The first phase module arm 11 and the second phase module arm 13 form a first phase module 15 of the power conversion device 1. The end of the phase module arm 11 facing away from the first AC voltage terminal 5 is electrically connected to the first DC voltage terminal 16. The end of the second phase module arm 13 facing away from the first AC voltage terminal 5 is electrically connected to the second DC voltage terminal 17. The first DC voltage terminal 16 is a positive DC voltage terminal, and the second DC voltage terminal 17 is a negative DC voltage terminal.

The second AC voltage terminal 7 is electrically connected to one end of the third phase module arm 18 and one end of the fourth phase module arm 21. The third phase module arm 18 and the fourth phase module arm 21 form a second phase module 24. The third AC voltage terminal 9 is electrically connected to one end of the fifth phase module arm 27 and one end of the sixth phase module arm 29. The fifth phase module arm 27 and the sixth phase module arm 29 form a third phase module 31.

The end of the third phase module arm 18 facing away from the second AC voltage terminal 7 and the end of the fifth phase module arm 27 facing away from the third AC voltage terminal 9. The end portion is electrically connected to the first DC voltage terminal 16. The end of the fourth phase module arm 21 facing away from the second AC voltage terminal 7 and the end of the sixth phase module arm 29 facing away from the third AC voltage terminal 9. The end portion is electrically connected to the second DC voltage terminal 17.

Each phase module arm has a plurality of modules 1_1, 1_2, 1_3, 1_4,..., 1_1n; 2_1,..., 2_n;...), which are electrically connected in series (due to their galvanic current connection). It is connected. Such modules are also called sub-modules. In the embodiment of FIG. 1, each phase module arm has n modules. The number of modules electrically connected in series by their galvanic current connections can vary greatly, preferably at least three modules are connected in series. However, for example, 50, 100 or more modules can be electrically connected in series. In this embodiment, n=36. Therefore, the first phase module arm 11 has 36 modules 1_1, 1_2, 1_3,..., 1_36. The other phase module arms 13, 18, 21, 27 and 29 are similarly constructed.

In the area on the left of FIG. 1, the control unit 35 for the modules 1_1 to 6_n is shown. From this central controller 35, optical information is transmitted to individual modules via optical communication links (eg, via fiber optic cables). The information transmission between the controller and a module is symbolically indicated by a line 37 in each case. The direction of information transmission is symbolically represented by the arrow on line 37. This is shown in the example of modules 1_1, 1_4 and 4_5. Information is sent to or received by the other modules in a similar manner. For example, the control device 35 sends to each individual module a target value for the height of the output voltage that each module should supply.

FIG. 2 illustrates the structure of one module 201. This module may be, for example, module 1_1 of the first phase module arm 11 (or it may be one of the other modules shown in FIG. 1). The module is configured as a half bridge module 201. The module 201 has a first on/off controllable electronic switching element 202 (on/off controllable switching element 202) having a first anti-parallel connected diode 204. Further, the module 201 is in the form of a second on/off controllable electronic switch element 206 (on/off controllable switch element 206) with a second anti-parallel connected diode 208 and a capacitor 210. Electrical energy storage device 210. The first electronic switching element 202 and the second electronic switching element 206 are each configured as an IGBT (insulated gate bipolar transistor). The first electronic switch element 202 is electrically connected in series with the second electronic switch element 206. A first galvanic module connecting portion 212 is arranged at a connection point between the electronic switching elements 202 and 206. A second galvanic module connecting portion 215 is arranged at the terminal of the second electronic switch element 206 on the side opposite to the connection point. Furthermore, the second module terminal 215 is connected to the first terminal of the energy storage 210. The second terminal of the energy storage 210 is electrically connected to the terminal of the first switch element 202 on the opposite side of the connection point.

Therefore, the energy storage 210 is electrically connected in parallel to the series circuit including the first switch element 202 and the second switch element 206. By appropriately controlling the driving of the first switching element 202 and the second switching element 206, the following is achieved: between the first galvanic module connecting portion 212 and the second galvanic module connecting portion 215. At, it can be achieved that the voltage of the energy store 210 is output, or no voltage is output (ie, zero voltage is output). Therefore, the desired output voltage of the power converter can be generated in each case by the cooperation of the modules of the individual phase module arms.

FIG. 3 shows another embodiment of one module 301 of the modular multilevel converter 1. This module 301 may for example be module 1_2 (or it may be one of the other modules shown in Fig. 1. First switch element 202, second switch element known from Fig. 2). 206, the first diode 204, the second diode 208 and the energy store 210, and the module 301 shown in FIG. 3 comprises a third diode 304 with an anti-parallel connected third diode 304. It has an electronic switch element 302 that can be turned on and off, and a fourth electronic switch element 306 that can be turned on and off and that includes a fourth diode 308 that is connected in anti-parallel. The second switch element 302 and the fourth switch element 306 capable of on/off control are each configured as an IGBT, unlike the circuit of Fig. 2, the second galvanic module connection portion 315 has a second switch. Instead of being electrically connected to the element 206, it is electrically connected to an intermediate point of an electrical series circuit including the third switch element 302 and the fourth switch element 306.

The module 301 of FIG. 3 is a so-called full bridge module 301. This full-bridge module 301 has a positive voltage of the energy storage device 210 between the first galvanic module connection 212 and the second galvanic module connection 315 when driving and controlling four switch elements accordingly. , Or a negative voltage of the energy accumulator 210 or a voltage of zero value (zero voltage) can be selectively output. Therefore, the full bridge module 301 can reverse the polarity of the output voltage. The power conversion device 1 may include only the half bridge module 201, only the full bridge module 301, or both the half bridge module 201 and the full bridge module 301. A large current of the power conversion device flows through the first galvanic module connecting portion 212 and the second galvanic module connecting portions 215 and 315.

FIG. 4 schematically shows an embodiment of the high-voltage DC transmission equipment 401. This high-voltage DC power transmission equipment 401 has two power conversion devices 1 as shown in FIG. Both power conversion devices 1 are electrically connected to each other via a high-voltage DC connection unit 405 on the DC side. Both positive side DC voltage terminals 16 of the power conversion device 1 are electrically connected to each other by a first high-voltage DC line 405a. The negative DC voltage terminals 17 of the power conversion devices 1 are electrically connected to each other by the second high-voltage DC line 405b. With this kind of high-voltage DC power transmission equipment 401, electric energy can be transmitted over a long distance. The high voltage DC connection 405 has a corresponding distance.

FIG. 5 shows an embodiment of the power conversion device 501 used as the reactive power compensation device 501. This power conversion device 501 has only three phase module arms 11, 18, and 27, and the phase module arms 11, 18, and 27 constitute the three phase modules 505, 507, and 509 of the power conversion device. doing. The number of phase modules 505, 507, 509 corresponds to the number of phases of the AC voltage system 511 to which the power converter 501 is connected.

The three phase module arms 11, 18, 27 are triangularly connected to each other . (The three phase modules 505, 507, 509 may be connected by star connection instead of triangular connection in another embodiment. In that case, the neutral point of the three phase module arms is The opposite ends are electrically connected to the phase lines 515, 517, and 519 of the three-phase AC voltage system 511. ) The power conversion device 501 supplies reactive power to the AC voltage system or reactive power. Can be taken out from the AC voltage system.

FIG. 6 shows a device 602 with an electrical energy store 210. The energy store 210, in this example, is an electrical capacitor 210, or more specifically, a unipolar electrical capacitor (having a positive side capacitor terminal (+) and a negative side capacitor terminal (−)). However, the energy store 210 may be a different type of capacitor, battery or accumulator in other embodiments. Device 602 may be, for example, module 1_2 (or it may be another module shown in FIG. 1). The device 602 shows the basic configuration of the module 201 shown in FIG.

The electrical energy store 210 is connected to the electronic circuit 612 (power electronics circuit 612) by the first electrical conductor 606 (first electrical connection 606) and the second electrical conductor 608 (second electrical connection 608). It is connected. The first electric conductor 606 is a positive-side electric conductor, and the second electric conductor 608 is a negative-side electric conductor.

The electronic circuit 612 includes a first electronic switch element 202, a second electronic switch element 206, a first antiparallel-connected diode 204, and a second antiparallel-connected diode 208. These are known from FIG. Further, the device 602 has a thyristor 616 connected in parallel with the electrical energy store 210. The thyristor anode 620 (anode terminal 620) is electrically connected to the first electrical conductor 606. The cathode 622 (cathode terminal 622) of the thyristor is electrically connected to the second electric conductor 608. The gate 624 (gate terminal 624) of the thyristor is unconnected in this embodiment. In other words, this gate 624 is open, i.e. not connected to other components. The thyristor 616 is a protective thyristor 616 that guides the discharge current 630 of the electric energy storage 210 when a failure occurs. The thyristor 616 serves as a bypass path for the electronic circuit 612 in the event of a failure and allows the discharge current 630 of the electrical energy store 210 to pass, thereby removing the (generally very large) discharge current of the electrical energy store 210 from the electronic circuit. Protect 612. Such a thyristor is also called a Crowbar-Thyristor. The discharge current 630 is also called a short-circuited discharge current 630 or a short-circuit current 630.

In the device 602, when a failure occurs, the next processing process proceeds. As a starting point, it is assumed that the electrical energy store 210 has been charged. Thyristor 616 is off (not fired), that is, thyristor 616 blocks current flow. Then, a failure occurs in the electronic circuit 612. For example (undesirably) the first electronic switching element 202 and the second electronic switching element 206 are simultaneously in a conductive state (formed by the first electronic switching element 202 and the second switching element 206). A so-called bridge short circuit occurs in the half bridge that is being used. This shorts the electrical energy store 210 and the discharge current 630 suddenly begins to flow.

The discharge current 630 first starts from the energy store 210 and flows via the first electrical conductor 606 to the electronic circuit 612. There, the discharge current 630 flows through the first electronic switching element 202 and the second electronic switching element 206. The discharge current 630 then returns to the energy store 210 via the second electrical conductor 608. In that case, the discharge current in the first electric conductor 606 and the discharge current in the second electric conductor 608 have opposite directions in each case. The discharge current 630 is limited only by the stray capacitance and ohmic resistance generated in the first electrical conductor, the second electrical conductor, and the electronic circuit 612. Therefore, the discharge current 630 increases relatively quickly.

Due to the (increasing) discharge current 630, a time-varying magnetic field is generated around the first electrical conductor 606. A time-varying magnetic field is also generated around the second electric conductor 608 based on the discharge current 630. Both of these magnetic fields overlap and both penetrate the thyristor 616 and thus the semiconductor material of the thyristor 616. That is, the thyristor is spatially arranged adjacent to the first electric conductor and the second electric conductor. (Thyristor 616 has an outer container made of a magnetic resistant material that does not interfere with, or only slightly interferes with, the magnetic field passing through thyristor 616.)

The time-varying magnetic field induces an electric current, for example an eddy current, in the semiconductor material of the thyristor. This current acts as a gate current (internal gate current) or a firing current, causing turn-on of thyristor 616 (ie, firing of thyristor 616). Due to the turn-on of thyristor 616, discharge current 630 now flows through thyristor 616, rather than through electronic circuit 612. More precisely, the discharge current 630 now flows from the energy store 210 through a portion of the first electrical conductor 606 to the thyristor anode 620 and from the thyristor cathode 622 to the second electrical conductor 608. Return to the energy store 210 via. The discharge current 630 flows through the thyristor 616. The reason is that the thyristor 616 is electrically connected to the energy storage 210 with low inductance. That is, the electrical connection between the thyristor 616 and the energy storage 210 is less electrically inductive than the first electrical conductor 606 and the second electrical conductor 608 that connect the energy storage 210 to the electronic circuit 612. Have.

Therefore, the thyristor 616 is turned on by the induced current (eddy current). In this case, the gate 624 is unconnected. The gate 624 need not be pulled out of the thyristor at all. The thyristor is turned on by the induced current (gate current), especially only when the temporal change of the magnetic field exceeds a certain threshold value. At that time, the temporal change of the magnetic field at a predetermined position of the semiconductor material of the thyristor is extremely important. With the semiconductor material of the thyristor, a particularly large temporal change of the magnetic field can be realized if the thyristor is placed very close to the first electrical conductor 606 and/or the second electrical conductor 608. The large temporal change of the magnetic field reduces the distance between the first electric conductor 606 and the second electric conductor 608, and the intermediate space between the first electric conductor 606 and the second electric conductor 608. It can also be realized by arranging the thyristor 616 in 635. In other words, when the temporal change in discharge current (in the first electrical conductor 606 and/or the second electrical conductor 608) exceeds a certain threshold, the induced current (gate current or ignition current). Turns on the thyristor. This threshold value is, for example, a value of 5 to 50 kA/μs.

The discharge current 630 flowing through the thyristor 616 causes the thyristor 616 to be thermally overloaded and thereby destroyed. Therefore, the thyristor acts as a sacrificial element to protect the electronic circuit 612 from the discharge current 630 in the event of a failure. Therefore, after the occurrence of a failure (ie, after discharging the discharge current 630 through thyristor 616), thyristor 616 must be replaced. In particular, the thyristor 616 has a so-called conduct-on-fail characteristic. That is, when a failure occurs (and also when it is destroyed by overload), the thyristor 616 remains conductive, and therefore the discharge current 630 can be led to the decay. Such thyristors with conduct-on-fail properties are commercially available.

As an alternative to a gate that is unconnected (or even not even pulled out of the thyristor), gate 624 may be terminated with a constant impedance not equal to zero. However, as another option, the next drive control unit may be connected to the gate. That is, in the drive control unit that supplies the gate current to the gate 624 of the thyristor at the time of failure without discharge (that is, at the time of failure without discharge of energy storage 210 or short-circuit discharge current 630 of energy storage). is there. A failure without this kind of discharge can be, for example, an overcharge of the energy store 210. This certainly does not lead directly to a short-circuited discharge current 630, but nevertheless must be prevented.

Another embodiment of the device 702 is shown in FIG. Device 702 may be, for example, module 1_2 (or it may be one of the other modules shown in Figure 1). The device 702 has the basic configuration of the module 301 shown in FIG.

The device 702 differs from the device 602 of FIG. 6 only in that the device 702 has an electronic circuit 712 that is different from the electronic circuit 612. The electronic circuit 712 additionally includes a third electronic switch element 302 with a third anti-parallel connected diode 304 and a fourth electronic switch element with a fourth anti-parallel connected diode 308. 306 and. The first electronic switch element 202, the second switch element 206, the third switch element 302, and the fourth switch element 306 are connected to a full bridge circuit. In the electronic circuit 712, for example, a failure may occur in which the third electronic switch element 302 and the fourth electronic switch element 306 are simultaneously conductive. The energy storage 210 is electrically short-circuited by the third switching element 302 and the fourth switching element 306, and the discharge current 630 starts flowing from the energy storage 210 to the electronic circuit 712. The further course of this process corresponds to the process described in connection with FIG.

FIG. 8 shows a device 802 of thyristors 616 between a first electrical conductor 606 and a second electrical conductor 608. The first electrical conductor 606 and the second electrical conductor 608 are here configured as a first current rail 606 and a second current rail 608. The first current rail 606 and the second current rail 608 each have a flat outer shape. Electronic circuitry 612 is shown as block 612 in the left portion of FIG. In the right part of FIG. 8, the energy store 210 is shown diagrammatically as block 210. Instead of electronic circuit 612, electronic circuit 712 can also be used.

The first electrical conductor 606 (first current rail 606) connects the energy storage 210 to the electronic circuit 612. The second electrical conductor 608 (second current rail 608) connects the energy storage 210 to the electronic circuit 612. A thyristor 616 is mechanically fixed between the first electric conductor 606 and the second electric conductor 608. Therefore, the thyristor 616 is in the intermediate space 635 between the first electrical conductor 606 and the second electrical conductor 608. The anode 620 of the thyristor 616 is in contact with the first electric conductor 606, and the cathode 622 of the thyristor 616 is in contact with the second electric conductor 608. The fixing is realized by the tightening device 806. The tightening device 806 has, in this embodiment, two bolts for fixing the first electric conductor 606, the thyristor 616 and the second electric conductor 608 with one nut each. The first electric conductor 606, the thyristor 616, and the second electric conductor 608 form a holding frame. This holding frame or mechanical fixing makes good electrical contact between the first electrical conductor 606 and the thyristor 616 and good electrical contact between the second electrical conductor 608 and the thyristor 616. Let Furthermore, the device is mechanically very stable on the basis of the fixed part or the holding frame, so that the device can reliably absorb the current force acting on the basis of a large discharge current.

It can be well recognized that the structural height of the thyristor 616 corresponds approximately to the spacing between the first electrical conductor 606 and the second electrical conductor 608. The anode 620 and the cathode 622 each form a clamping surface of the thyristor 616. The magnetic field lines of the magnetic flux density B run parallel to the tightening surface of the thyristor 616 (not shown in FIG. 8; see FIG. 10). The electric field (E field) is perpendicular to the field of magnetic flux density B, but not shown. For example, a discharge current 630 that increases very rapidly from 0 to about 20 kA allows the thyristor 616 to turn on, ie, have a maximum value greater than about 20 kA and a very short time (1 μs to 2 μs or less). The discharge current increasing to its maximum value causes the turn-on of thyristor 616.

The thyristor 616 has the shape of a disk cell in the embodiment of FIG. The thyristor 616 has a disk cell container. In other words, the thyristor has a disk-shaped structure, with the bottom surface serving as the cathode and the top surface serving as the anode. By using such a disc-cell-shaped thyristor, a mechanically stable holding frame can be realized. The display of FIG. 8 further shows that the thyristor gate 624 is unconnected. Unlike the display of FIG. 8, the gate 624 need not even be pulled out of the container 810 of the thyristor 616. The reason is that the gate is unconnected.

FIG. 9 shows the device 802 according to FIG. 8 in a side view. Here, the periphery of the disk cell-shaped thyristor 616 is indicated by a broken line.

FIG. 10 shows the device 802 in plan view, similar to the display of FIG. However, in FIG. 10, the fastening device 806, the container of the thyristor 616, the electrical connection between the anode and the first electrical conductor, the electrical connection between the cathode and the second electrical conductor are omitted. Has been done. Only the semiconductor material 1006 of thyristor 616 is shown. This semiconductor material 1006 forms one disk 1006 (disk-shaped semiconductor material 1006, semiconductor material disk 1006). Disk 1006 is shown in cross-section. In side view, the disk 1006 has a circular contour similar to that around the thyristor in FIG. The semiconductor material 1006 is shown too thick for reasons of clarity. The important semiconductor structure (in particular, the silicon structure) in the semiconductor material 1006 is often very thin, for example, a thickness of several hundred μm.

Furthermore, the magnetic force lines of the magnetic field 1010 (the magnetic force lines 1010 of the magnetic flux density B) formed in the intermediate space 635 between the first electric conductor 606 and the second electric conductor 608 are shown. The magnetic field lines 1010 of the magnetic field emerge from the plane of the drawing and face the observer. The observer looks, so to speak, from the front toward the tip of the magnetic field line. Since the first electric conductor 606 and the second electric conductor 608 are plate-shaped, parallel magnetic field lines 1010 are formed in the intermediate space 635 between the first electric conductor 606 and the second electric conductor 608. It The magnetic field lines 1010 penetrate the semiconductor material 1006 of the thyristor. A voltage 1016 is induced in the semiconductor material 1006 due to the time-varying magnetic field 1010, which causes a current 1018 (eddy current 1018) to flow in the semiconductor material 1006 of the thyristor. Voltage 1016 and current 1018 are shown here only schematically. The induced current 1018 acts as a thyristor gate current 1018 or a thyristor firing current, turning on the thyristor 616 (ie, the current 1018 ignites the thyristor 616).

The first electrical conductor 606 has a first flat outer surface 1024. The second electrical conductor 608 has a second flat outer surface 1026. The first flat outer surface 1024 and the second flat outer surface 1026 are arranged parallel to each other. The disc-shaped semiconductor material 1006 of the thyristor 616 is arranged parallel to the first outer surface 1024 and likewise parallel to the second outer surface 1026. This arrangement of semiconductor material 1006 enables a compact, mechanically stable construction of device 802. In addition (due to the possible small spacing between the first and second electrical conductors 606, 608), a large temporal change in the magnetic field at the position of the semiconductor material 1006 is produced.

In other words, the disc 1006 (thyristor silicon wafer 1006) is a conductive material. As soon as the disc is penetrated by the time-varying magnetic field 1010, a current 1018 (in particular an eddy current) is generated in the plane of the disc. This current causes the thyristor 616 to fire, or turn on. The greater the flowing short-circuiting discharge current 630, the greater the magnetic flux density B produced thereby.

FIG. 11 once again illustrates, by means of a flow chart, a method of discharging the energy store 210. At the starting point of this method, the energy store is charged and the thyristor is turned off (blocked).

Method step 1102:
After a failure occurs in the electronic circuit 612, the discharge current of the energy storage device 210 starts to flow. A discharge current 630 flows from the energy store 210 via the first electrical conductor 606 to the electronic circuit 612 and returns to the energy store 210 via the second electrical conductor 608.

Method step 1104:
Due to the increasing discharge current 630, a time-varying magnetic field 1010 is generated around the first electrical conductor 606 and/or the second electrical conductor 608, and the semiconductor material 1006 is penetrated by the magnetic field 1010.

Method step 1106:
The time-varying magnetic field 1010 induces a current in the semiconductor material 1006 of the thyristor 616. Current 1018 acts as a thyristor gate or firing current.

Method step 1108 :
The induced current 1018 turns on thyristor 616. Accordingly, the energy storage 210 discharge current 630 flows through the thyristor 616, thereby bypassing the electronic circuit 612.

Method step 1110:
As the discharge of the energy storage 210 increases, the discharge current 630 decays.

A method in which a magnetic field coupled to the thyristor (more specifically, a magnetic flux density B coupled to the thyristor) penetrates the entire thyristor and generates an induced current (eddy current) in the thin semiconductor structure/semiconductor material of the thyristor. And the device. This current causes a gate current (or ignition current) to flow in the semiconductor material above a threshold of the time-varying magnetic field (dB/dt), thereby (requiring an external gate current from an external electronic evaluation circuit). Sufficient to turn on the thyristor (without doing so). Therefore, no external control of the gate is required, and fault/short circuit recognition is inherent in the thyristor, as long as the thyristor is not damaged. This is a great advantage. This is because the functional test of the evaluation circuit is difficult and expensive in reality in the case of a large capacity energy storage device. In particular, the device and the method have a low failure rate (FIT-Rate), which corresponds approximately to the failure rate of thyristors. This failure rate is very low for thyristors.

In the device and method described above, the short-circuit discharge current 630 of the energy store is used for the delay-free firing of the thyristor, which would result in a time delay. Alternatively, no evaluation circuit is needed. The technical realization with only one thyristor is extremely simple and cheap. Upon ignition of the thyristor, it must be destroyed (depending on the amount of energy to be controlled by the energy store) and possibly replaced during later maintenance. A relatively simple diode disk cell container is used for the thyristor. This is because the gate terminal 624 is not needed and therefore need not be pulled out of the container.

In the above-mentioned device and in the above-mentioned method, no appreciable heat losses occur, which clearly improves the energy efficiency compared to the protective elements which also generate conduction or switching losses during normal operation. To do. As a result, the electrical losses of installations with a large number of the above-mentioned devices (for example high-voltage DC transmission installations) are kept slightly, which leads to significant cost savings.

Described is an apparatus and method that can safely and reliably discharge an electrical energy store, especially during a short circuit. Advantageously, it requires no additional components other than one thyristor. This allows a very simple and reliable protection of the electronic circuit from the discharge current of the energy store.

1 Power converter (multi-level converter)
1_1 to 6_n module 202 first switch element 206 second switch element 210 electrical energy store 302 third switch element 306 fourth switch element 606 first electrical conductor 608 second electrical conductor 602 device 612 Electronic circuit 616 Thyristor 620 Anode 622 Cathode 630 Discharge current 702 Device 712 Electronic circuit 810 Disk cell container 1006 Semiconductor material 1010 Thyristor semiconductor magnetic field 1018 Time-varying magnetic field 1018 Induced current

Claims (16)

A method of discharging an electrical energy store (210) connected to an electronic circuit (612) by a first electrical conductor (606) and a second electrical conductor (608), said energy store ( 210) is provided with a thyristor (616) for discharging
Due to a fault occurring in the electronic circuit (612), a discharge current (630) of the energy store (210) is transferred from the energy store (210) via the first electrical conductor (606). Begins to flow into an electronic circuit (612) and returns to the energy storage (210) via the second electrical conductor (608),
A time-varying magnetic field (1010) is generated around the first electrical conductor (606) and the second electrical conductor (608) based on the discharge current (630), and the temporally varying magnetic field (1010) is generated. A changing magnetic field (1010) penetrates the semiconductor material (1006) of the thyristor (616),
The time-varying magnetic field (1010) induces a current (1018) in the semiconductor material (1006) of the thyristor,
The method wherein the induced current (1018) turns on the thyristor (616). The method of claim 1, wherein the electronic circuit (612) comprises at least two electronic switching elements (202, 206) arranged in a half bridge circuit. The electronic circuit (712) includes the two electronic switch elements (202, 206) and two other electronic switch elements (302, 306), and the two electronic switch elements (202, 206) 3. The method according to claim 2 , characterized in that the two other electronic switching elements (302, 306) are arranged in one full bridge circuit. An electronic circuit (612), an electrical energy store (210), and a thyristor (616) for discharging the energy store (210), the energy store (210) being the first A device (602), which is connected to the electronic circuit (612) by an electrical conductor (606) and a second electrical conductor (608),
The thyristor (616) is as follows:
Generated based on the discharge current (630) of the energy store (210) flowing through at least one of the first electrical conductor (606) and the second electrical conductor (608), the thyristor (616) Such that a current (1018) that turns on the thyristor is induced in the semiconductor material (1006) of the thyristor based on a time-varying magnetic field (1010) that penetrates the semiconductor material (1006),
Device (602), characterized in that it is arranged spatially adjacent to at least one of said first electrical conductor (606) and said second electrical conductor (608). The thyristor (616) is arranged in an intermediate space (635) between the first electrical conductor (606) and the second electrical conductor (608). Equipment. An anode (620) of the thyristor is connected to the first electric conductor (606), and a cathode (622) of the thyristor is connected to the second electric conductor (608). The device according to claim 4 or 5. 7. The thyristor (616) is mechanically fixed between the first electrical conductor (606) and the second electrical conductor (608). The apparatus according to item 1. Device according to any one of claims 4 to 7, characterized in that the thyristor (616) comprises a disk cell container (810). 9. At least one of the first electrical conductor (606) and the second electrical conductor (608) is formed as a current rail, respectively, according to any one of claims 4 to 8. apparatus. At least one of the first electrical conductor (606) and the second electrical conductor (608) has a respective flat outer surface, the semiconductor material of the thyristor forming a disc (1006), the disc (1006) Device according to any one of claims 4 to 9, characterized in that it is arranged parallel to at least one of the flat outer surfaces (1024, 1026). 11. Device according to any one of claims 4 to 10, characterized in that the thyristor (616) is connected to the energy store (210) with low inductance. Device according to any one of claims 4 to 11, characterized in that the thyristor (616) is connected in parallel with the energy store (210). 13. Device according to any one of claims 4 to 12, characterized in that the electronic circuit (612) comprises at least two electronic switching elements (202, 206) arranged in one half-bridge circuit. .. The electronic circuit has two electronic switching elements (202, 206) and two other switching elements (302, 306), and the two electronic switching elements (202, 206) and the two other switches. 14. Device according to any one of claims 4 to 13, characterized in that the elements (302, 306) are arranged in one full-bridge circuit. Having a device according (602, 702) in any one of claims 4 to 14, modular module multilevel converter (1) (1_1,1_2, ..., 6_n). A module-type multilevel converter (1) having a large number of modules (1_1, 1_2,..., 6_n) according to claim 15.

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